The pilot generator creates a millivolt electric current which is enough to operate the gas valve and the pilot safety circuit. The control switch interupts the current to the gs valve, just as a thermostat would in a heating system, and turns the burner off.

: I have a gas fireplace with a gas control valve. The valve operates without a 115V or 28V source. All it needs is a switch closure and a pilot to turn it on. The book calls it a millivolt control. How does this device work?